Contact lenses have gained wide acceptance in correcting many forms of vision deficiencies. These lenses have generally been made of relatively rigid materials such as plastics which are well suited for contact lens use.
However, one of the principal disadvantages of the conventional rigid corneal contact lenses is the discomfort they induce in the upper eyelid lining as the lid slides over the edge of the lens during a blink. Attempts to grind this edge to a thin featheredged configuration has posed the serious danger of laceration of the ocular area.
It was discovered that certain soft materials such as polymeric hydrogels made by polymerizing a catalyzed mixture of acrylates and/or methacrylates of polyhydric alcohols are also well suited for use in preparing contact lenses. See, generally, the disclosure U.S. Pat. No. 2,976,576. This development was a partial solution to the problem of eyelid discomfort to the wearer, whereby the soft texture of the lens enabled the edge to be made thinner and to lie closer to the surface of the eye.
However, a major limitation of the soft lenses is that their flexible nature makes them more subject to physical distortion and, hence, somewhat deficient for the correction of vision and particularly of corneal astigmatism. The flexible character of the soft lens allows the corneal defects to be transmitted through the lens itself. As a consequence, the front surface of the lens does not remain spherical and thereby does not sufficiently correct the wearer's vision.
The improved lens of the present invention, therefore, provides a corneal contact lens which will retain a spherical configuration or other specified shape once imparted to the central optical area, yet possessing a soft, flexible, feather-edged periphery thereby providing optical superiority combined with a safer and more comfortable fit for the eye.